It is proposed to continue research and development aimed at improved understanding of mechanisms and rational application of counterpulsation. Utilizing the previously evolved criteria for phasing diastolic augmentation and end diastolic/systolic sink in aortic pressure, experimental effort is now directed at assessing the effects of circulatory assistance on cardiac function of ischemic and nonischemic regions and on preservation of jeopardized myocardium. An improved closed chest intracoronary plug occlusion model will be applied to provide longer experiments, to simulate more complex multiple, sequential and/or gradual coronary occlusions, and to study infarct size through detailed histopathology. Intraaortic Balloon Pumping and Ascending Aorta Synchronized Pulsation will be evaluated in various postocclusion states including cardiogenic shock. The potentials of a newly developed technique of synchronized diastolic augmented coronary venous retroperfusion technique will be examined. Phased retrograde coronary venous drug infusions and evaluation of counterpulsation with potentially promising pharmacologic interventions will have a common objective of maximizing the benefits to acutely ischemic and border zones of the heart. An alternate intraaortic balloon pumping system will be studied to resolve questions relating to balloon dynamics.